OS 10.4x - Booting Linux PPC from a USB Drive on my PowerBook

Not sure if anyone will know the answer to this, it's sort of a Linux question. I'm a Mac user but use Linux a bit on my PC. I've never run Linux on my PowerBook G4 before. I recently purchased a drive kit so I connected my old 8gb hard drive to my PowerBook using USB which works great. The device only has USB, not Firewire. When I boot up my Mac and hold down option, it shows my main hard drive, and the Ubuntu Linux boot CD, but not the hard drive. I figured this is normal since it's empty. I booted off the CD, the ubuntu installer detected the USB drive and installed Linux to it no problem. When it went to install the yaboot boot loader, it gave an error. This is fine because I don't want to have a boot loader, I was hoping I could just hold down option when I boot and click the USB drive to boot to Linux. However, it still doesn't show the drive, even though Linux is on it and bootable. Is this normal? Will it only show firewire or internal drives? Is there some solution to this, even a boot loader I can boot off a CD or something then choose it? Not sure where to look for help, thanks so much.

This is normal, it is not showing up because USB is too slow to boot off of. You have two solutions to this 1. back everything up wipe your hard drive and make it dual boot of Linux and Mac 2. Buy a firewire drive (you can boot from firewire)

Or copy ubuntu to your ibook's internal drive, reboot it and hold down 't' about 20 seconds and then reboot the powerbook, hold down option and select the ubuntu installation on the ibook as a boot folder.

I'm just confused as to why it's too slow. I know firewire is typically faster since its a constant transfer rate at 400mbps, but with nothing running shouldn't usb be 480mbps? Either way where I'm confused is that the ubuntu CD detected the USB drive and installed to it without a problem. When it couldn't install yaboot it said to boot manually using root=/dev/sda3. I'm not THAT good in Linux to know what that means, but is there no way to force it to boot by passing parameters to the kernel off the CD or some other method?

You always need a bootloader to load an operating system. There are bootloaders for BIOS and bootloaders for EFI. They are looked for differently. Mac uses EFI, though it does have a BIOS compatibility module that can make the EFI look and act like a BIOS. What triggers the Mac to list a drive with a BIOS bootloader as an option (to then boot through the compatibility layer), I don't know.
But I can send you down the path of understanding:

As far as root=/dev/[whatever], that's setting the root directory. You're making that be where the bootloader is looking. You are picking a partition to be pointed at. The Linux kernel (heart of the operating system) makes files to represent hardware that programs can use standard read/write functions calls to send and receive data to/ from. The kernel intercepts this and passes it on to the hardware from the program or from the hardware to the program. The file that represents the whole drive could be /dev/sda. /dev/sda1 would be it's first partition. Sda is scsi disk A (first scsi disk), sdb is scsi disk B (second scsi disk), etc.
Cheers,
Jake